Includes door pairs that can be only open one at a time, such as an airlock. Often incorporating pressurisation, scanning and decontamination capabilities. Pseudo-puzzles in games where these are unexpected and both doors need to be manually operated.
The first video game about Airlocks was released on August 11, 1999.
Commonly seen as part of research facilities, medical facilities (for highly contagious diseases), spacecraft, space stations, submarines and other watercraft, some military bases (for screening and containing any intruders), and so forth.
This tag is usable regardless if the airlock is actually air tight or anything, as long as it serves a similar function.